Platform system for greenhouse roof

ABSTRACT

A platform system useful for constructing, maintaining, or repairing greenhouse roofs comprises a platform section providing a working area surface formed with removable treads supported on left and right platform rails. The platform section is supported by downwardly projecting upper and lower support bases appointed to rest on structural members of the roof, thereby providing a clearance between the working area surface and the roof beneath. Guardrails extend along the sides of the platform section between guardrail posts attached at the upper and lower ends of the platform rails. The system is light-weight, minimizing the loading imposed on the roof and permitting it to be readily positioned by a small work crew. The support base may include retractable rollers that permit it to be slid upward across the eaves and onto the roof. A deployment assist cart may be used to erect, support, and access the platform system.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 62/053,277, filed Sep. 22, 2014, and entitled “Platform SystemFor Greenhouse Roof,” which is incorporated herein in its entirety forall purposes by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a platform useful for safelyconstructing, maintaining, and repairing the roofs of greenhouses andother like building structures, which are relatively fragile and cannotsustain excessive loads.

TECHNICAL BACKGROUND

Greenhouses have long been used to provide a controlled climate forgrowing plants. Typically a greenhouse includes a skeletal structuremade of metal (or possibly wood) supporting a roof formed of a materialthat is transparent to light but impervious to the passage of air orprecipitation. Glass and plastic or polymeric materials are commonlyused. Often the same materials are used to construct some or all of thewalls of the greenhouse.

Light from the sun incident on a greenhouse includes radiation in bothvisible and infrared (heat) wavelengths. Some of this light passesthrough the walls and roof and is absorbed, heating the interior of thegreenhouse and its contents. The walls and roof provide a closedconstruction that minimizes loss of that heat through unwantedcirculation of the interior air to the exterior. Plants grown in agreenhouse can thus be kept warmer than they would be if simply situatedin ambient air. Sometimes natural light is supplemented by artificiallight. The inside air can also be heated and/or cooled and may becirculated by fans.

Greenhouses are used worldwide for a number of purposes, including theiruse to extend the typical growing season at both ends for plants and topermit plants to be cultivated in a given climate zone in which theyotherwise could not be sustained. For example, in temperate climates,plants can be started from seed much earlier in the spring and maycontinue to produce flowers or fruit much later into the fall than theyotherwise would. Many greenhouses are used to raise plants on acommercial scale that are either ornamental or produce edible fruits orvegetables. Greenhouses are also used to raise exotic or tropical plantsfor display in botanical gardens or to provide such plants to florists,and for horticultural and other botanical research projects.

Greenhouses are found in many configurations. For some, such as those inbotanical parks and other public spaces, aesthetic appeal is a paramountdesign factor, so architects have included intricate, multi-planar orcurvilinear roof shapes. On the other hand, utilitarian factors such asefficiency and minimizing costs of construction, operation, andmaintenance govern the vast majority of designs for commercialgreenhouses. The smallest sizes are sometimes built with a simple metalframe structure covered with a flexible film of material such aspolyethylene. However, this construction has limited durability andresistance to wind and precipitation (rain, snow, hail, etc.), so roofsof larger commercial structures are commonly built with simple shapeshaving a limited number of large, planar surfaces formed with rigidpanels of glass or comparable plastic materials.

For example, a common greenhouse structure is depicted generally at 10in FIG. 1. Greenhouse 10 has side supporting walls 20 and end or gablewalls 21. The roof configuration shown is frequently termed a pitched orsloped roof; it includes two large, planar, sloped sides 12 that join atan apex 14 to form a configuration having the shape of an inverted vee,when viewed from an end wall. A skeletal structure includes a series ofrafters 16 that extend on both sides between a ridge beam 18 and eaves19, which are formed at the junction of roof side 12 and thecorresponding side supporting wall 20. Wall supports 17 are included inboth side and end walls 20, 21. One or more cross members 22 runtransverse to, and are supported by, rafters 16. Often, some or all ofrafters 16 form part of a truss structure (not shown) as required tosupport a preselected design load. Ordinarily, the design load accountsfor: the static structure of the building and its appointments; wind andsnow loading; and incidental loading (often termed “live loading”), suchas that resulting from workers servicing the roof.

The horizontal spacing between adjacent rafters 16 is ordinarilygoverned by the size of glass panels 26 that can be effectivelysupported just at their lateral edges 30 at the selected roof pitch. Ina common configuration, the glass panels are installed in a shingledfashion, beginning from the eaves upward toward the ridge, with eachsuccessive ascending panel being lapped slightly over its lowerpredecessor to minimize the intrusion of precipitation and wind. Theglass panels may be secured using a technique apparent in the detailed,cross-sectional view of FIG. 2. The lateral edges 30 of panels 26 arereceived in channels of an elastomeric, compliant gasket structure orcaulking 36. The gasketing in turn is sandwiched between a rafter (hereshown as a box beam 34) and a glazing bar 32 mounted above, and runningparallel to, beam 34. Together, the box beam 34 and the attached glazingbar 32 are frequently termed a purlin. A fastener, such as screw 40 witha corresponding elastomeric sealing washer 42, secures the glazing bar32 and the glass panels 26. The glazing bars 32 can be readily removedto allow replacement of glass panels 26.

Frequently a ridge vent (not shown) is created at or near the ridge beam18; it may be selectively openable to permit adjustment of theventilation in the building. In some designs, some or all of the glasspanels adjacent the ridge are mounted in openable frames to provide theventilation. Additional glass panels elsewhere in the roof may also bemade openable for additional ventilation. The structural members arealmost always metal, although wood or other materials could be used.

Larger greenhouses are sometimes constructed by joining additional pairsof roof sections that alternate in slope, a form sometimes termed “ridgeand furrow.” For example, a configuration having the shape of aninverted letter “W” (as seen in end view) could be formed using fourplanar sections. Such construction provides a structure having increasedwidth, while maintaining the slope angle of the individual sections, butwithout increasing the overall height, as would be required for a singlevee-shaped structure of the same roof slope and width.

It will be understood that the term “glass” is used herein to refereither to conventional glass panels of the types used ubiquitously inconstruction or to other frangible, transparent or translucent panelmaterials such as poly(methyl methacrylate) (e.g., PLEXIGLAS®) andpolycarbonate (e.g., LEXAN®) that are also commonly used. Greenhousesare commonly constructed with ordinary soda-lime window glass, but moreadvanced tempered and laminated safety glasses are sometimes used. Theseadvanced glass and plastic materials typically cost more but afford someadvantages of improved safety and durability.

Society has increasingly recognized the importance of providing safetysystems and equipment to mitigate or prevent injury to workers duringbuilding construction, operation, and maintenance. The prevalence ofinjuries in the past has prompted industry to voluntarily improve itsown standards and practices. Regulations have also been imposed bygovernmental agencies. In general, safety practices that address theserequirements are known and relatively easy to implement in manyconventional construction and later maintenance and repair operations.However, the extensive use of frangible materials like glass ingreenhouse roofs presents significant challenges that go beyond what isencountered with other, more common building types. For example, thehazard of falling off a roof is common to all buildings, but a worker ona greenhouse is additionally vulnerable to falling through a glass roofpanel and being lacerated by broken glass or injured by hitting internalstructural members or a hard ground surface attendant to the fall below.An even greater potential for serious, even life-threatening, injury isapparent.

Inevitably, glass roofs are vulnerable to damage during construction andduring their ordinary use, whether resulting from inadvertent humanactions or from external causes, like hail or other falling objects.Post-construction repairs often must be done quickly and under adverseconditions, which typically heighten the likelihood of accidents.

Repairs are sometimes made from a suitably positioned cherry pickercrane that provides a worker access from a platform suspended above awork area. However, implementing this approach is typically costly, anda suitable ground location for the cherry picker close enough to theroof area may not be available.

Thus, workers often resort to planks or ladders placed directly onto theroof structure to form a makeshift working surface from which a workercan perform required repairs. However, these approaches do not affordacceptable safety, as safety equipment and precautions effectively usedfor conventional buildings are inadequate, inapplicable, or inoperable.

For example, fall protection is ordinarily required for persons such asroofers working more than a few feet off the ground. In some instances,railing systems associated with scaffold platforms or ladders areadequate, but often, workers must have mobility that makes these systemsdifficult or impossible to implement, so other approaches are needed.

Although various safety equipment and methods are known, including thosedescribed above, there nevertheless remains a need for systems thatfacilitate construction and repair of roofs of greenhouses and otherbuildings.

SUMMARY OF THE INVENTION

An aspect of the invention relates to a platform system elongated alonga platform length direction between a lower end and an upper end andhaving opposing left and right sides separated along a platform widthdirection, the platform system being configured for placement on a roofstructure and comprising:

(a) left and right upper-end guardrail posts and left and rightlower-end guardrail posts;

(b) a platform section that extends along the platform length directionfor a platform length and comprises:

-   -   (i) left and right platform rails that are disposed in        spaced-apart, parallel relationship and extend horizontally        along the length of the platform section between the upper and        lower ends of the platform system, the upper-end guardrail posts        and the lower-end guardrail posts being attached to the        respective platform rails,    -   (ii) a plurality of platform treads disposed along at least a        portion of the platform length, each tread having left and right        edges and spanning the left and right platform rails and being        removably secured thereto, the treads collectively defining a        working platform area having a platform width sufficient to        accommodate a worker and a preselected working length defined by        the number of treads present, and    -   (iii) left and right guardrails that extend horizontally along        the respective sides of the platform system for substantially        the platform length, are attached to the respective left and        right platform rails through the lower and upper guardrail        posts, and are situated at a preselected height above the        platform area;

(c) an upper support base proximate the upper end and comprising anupper horizontal member; and

(d) a lower support base proximate the lower end and comprising a lowerhorizontal member, and wherein the upper and lower support bases projectdownward from the platform section and are configured to rest on theroof structure to support the platform system and maintain a clearancebetween the roof structure and the platform section.

In some implementations, the present platform system is modularized,comprising a plurality of constituent parts or subassemblies that may beassembled and disassembled repeatedly. Modular construction facilitatesconvenient transportation and storage of the system, and permits theplatform system to be adapted so it can be used to access roofs ofdifferent sizes and configurations.

Another aspect provides a platform erection system wherein the presentplatform system is used in conjunction with a deployment assist cartthat comprises:

(a) a platform base section;

(b) a deployment support upstanding from the platform base section;

(c) deployment rails connected to the deployment support and configuredto receive the platform system for deployment on the roof structure.

In an implementation, the deployment rails are rotatable between aloading position configured to accept the platform system and adeployment position configured to permit the platform system to bemaneuvered from the deployment rails onto a surface of the roofstructure. The deployment assist cart is beneficially employed in any ofthe transportation, erection, and support and stabilization of theplatform system on a roof structure.

A further aspect provides a kit that comprises parts that, whenassembled, are capable of forming the platform system of the presentdisclosure. In another implementation, the kit further comprises partsthat, when assembled, are capable of forming the present deploymentassist cart, which is configured to receive the platform system fordeployment on a roof structure.

A still further aspect provides a method that provides access to astructure that may, without limitation, be a greenhouse roof structure.The method comprises providing the platform system of the presentdisclosure and disposing the platform system on a flat or sloped area ofthe structure, whereby access is provided to the area.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be more fully understood and furtheradvantages will become apparent when reference is made to the followingdetailed description of certain of the preferred embodiments and theaccompanying drawings, wherein like reference numerals denote similarelements throughout the several views and in which:

FIG. 1 depicts in perspective view a schematic form of a conventionalgreenhouse having a pitched roof;

FIG. 2 depicts in a detailed, cross-sectional view (taken at 2-2 inFIG. 1) a conventional attachment of glass roof panels to a supportingrafter using a glazing bar;

FIG. 3 depicts in perspective view a schematic form an implementation ofthe present platform system;

FIG. 4 depicts in side elevation view a tread attachment used in anembodiment of the present platform system;

FIGS. 5A-5B depict details of one possible tread attachment employed tosecure platform treads to the platform rails of an embodiment of thepresent platform system; FIG. 5A is a top plan view of a portion on theleft side of the platform system and FIG. 5B is a cross-sectional viewtaken at 5B-5B in FIG. 5A;

FIGS. 6A-6B depict in perspective view a roller assembly that includes aspring mechanism employed in an embodiment of the present platformsystem, with the roller depicted in its retracted and extended positionsin FIGS. 6A and 6B, respectively;

FIG. 7 depicts an inclined platform tread included in an embodiment ofthe present platform system, taken in side elevation view;

FIG. 8 depicts in perspective view a modular platform systemof thepresent disclosure;

FIG. 9 is an enlarged perspective view of a portion of FIG. 8, showingschematically the connection system used to join the modular componentsof the FIG. 8 platform system embodiment;

FIG. 10 depicts in perspective view the modular assembly of multipleplatform subsections to form a platform system in accordance with anaspect of the present disclosure;

FIG. 11 depicts in perspective view a deployment assist cart used inaccordance with an aspect of the present disclosure; and

FIGS. 12A-12C depict in side elevational view stages of the erection ofthe platform system onto a roof using the deployment assist cart of FIG.11.

DETAILED DESCRIPTION

An aspect of the present disclosure addresses the need for a platformsystem that allows a worker to construct and maintain roofs safely andconveniently, including especially the sloped roofs of greenhouses andlike structures that are constructed of glass or other fragilematerials. Embodiments of the platform system have a configuration thatis adaptably sized and can be placed onto the roof, with the loadingsupported on appropriate structural members of the roof system. Theplatform system can be configured to permit a worker to easily accessspecific glass panels of a greenhouse roof for repair or replacementwhile providing a greatly improved level of security and protection.

Generally stated, embodiments of the present platform system include oneor more of: (i) a platform section comprising a working surface havingan adjustable working length; (ii) a railing system on one or both sidesof the platform that protects a worker from inadvertently falling offthe platform; (iii) support bases that allow the platform system to besupported with a clearance maintained between the working surface andthe underlying roof; and (iv) anchorage points to which a worker's fallarrest system can be reliably secured. The platform system ordinarily isdisposed on a sloped roof with its lower end approximately at the eavesof the roof and with its length direction extending along a line towardthe roof ridge. It facilitates convenient and immediate access to anydesired area of a roof structure underneath the platform system oradjacent to it.

The platform system is described herein with principal reference to itsuse in constructing and repairing glass-roofed greenhouses. However, itwill be understood that embodiments of the platform systems providedherein are equally useful with roofs constructed with other fragilematerials (e.g., slate or terra cotta tile) not capable of sustainingsignificant loads by themselves. More generally, the platform system andthe optional deployment assist cart herein could be used beneficially inany other situation in which access to a horizontal or sloped area of astructure is desired but it is preferred, or probably necessary, thatthe loading that results be applied only in defined points or regionsoutside that immediate horizontal or sloped area.

The present platform system beneficially includes removable platformtreads. They are ordinarily installed beginning at the lower end, withthe total number of treads being preselected to provide access anddefine a working surface that extends just up to the roof area to beserviced, without obscuring it. Thus, the platform system provides greatflexibility, with the working surface appointed to allow a worker towalk or crawl to gain access to the area of interest, and to sit, kneel,or lie close enough to carry out required activities in that areasafely, conveniently, and comfortably. In an embodiment, the platformarea and the associated platform treads are approximately 30 inches (75cm) wide to afford easy passage and positioning of the worker, but otherdimensions are also possible. Although not required, the platform systemis typically constructed in sections that are at least 5 feet (1.5 m)long, but sections constructed in any convenient length, such as 10, 15,or 20 feet (3, 4.5, or 6 m) or more are also possible, especially iffabricated with lightweight materials that facilitate easy handling, asdescribed in more detail below.

The terms “horizontal” and “vertical” are used herein to describe, inthe conventional sense of those terms, the orientation of certainstructural members of the present platform system when it is resting ona level, flat surface. Vertical members are thus ones that extend in adirection perpendicular to the plane of the level surface; horizontalmembers extend parallel to the plane of the level surface, and includeones oriented along either the platform length direction (e.g., platformrails 56 and guardrails 58 shown in FIG. 3) or the platform widthdirection (e.g., platform treads 78 and horizontal members 60, 61 ofFIG. 3). (Of course, when the platform system is placed on a sloped roof(also termed a “pitched roof”), the horizontal components that extendalong the platform length direction become inclined at an angle thatgenerally conforms to the angular pitch of the roof and the verticalcomponents are oriented in a direction generally perpendicular to theplane of the roof.)

The present platform system and the working area provided thereby aredescribed as elongated, meaning that they extend horizontally along aplatform length direction with a platform length dimension that isordinarily greater than a corresponding horizontal width dimensionmeasured across the platform working area in a platform width directionperpendicular to the platform length direction. Hence, the platformsystem and certain components thereof are described as having “upper”and “lower” ends, which refer to the respective ends that are higher andlower in elevation when the system is disposed with its length extendinggenerally along a direction between the eaves and the ridge of a slopedroof structure. Of course, other placements on a roof are also possible.Unless otherwise specified, “left” and “right” are used in reference tothe sides of the platform system when viewed along the length directionfrom the lower end. As used herein, the term “working area” refers tothe area of the present platform system that is accessible andconfigured to permit a worker to walk, stand, sit, kneel, or the like inthe ordinary course of using the system. In general, the working area isprovided by removable platform treads, though there may also beancillary or peripheral areas that provide some additional amount ofaccessible space but are not covered with removable treads. The “fullworking area” is defined as the working area afforded when platformtreads are installed in all available positions between the ends of theplatform rails, whereby worker access is provided along the entirelength of the platform system.

The present platform system and its various components may beconstructed of any suitable structural materials that afford therequisite strength and other mechanical properties. Certain embodimentsemploy lightweight materials to minimize the loading imposed onstructures on which the platform is situated during its ordinary use.

One possible embodiment of the present platform system is depicted byFIG. 3. Platform system 50 includes a platform section 52, whichcomprises left and right platform rails 56 that extend substantially thefull length of the platform section, left and right guardrails 58,upper-end guardrail posts 68, and lower-end guardrail posts 70. In theembodiment of FIG. 3, the guardrail posts 68, 70 are attached toplatform rails 56 through intervening structural members included inupper and lower support bases 79, 80. Other configurations that provideattachment of the guardrail posts to the platform rails, eitherdirectly, or indirectly through intervening members, are alsocontemplated.

One or more platform treads 78 span the left and right platform rails.In the FIG. 3 implementation, the treads are supported at each side byflanges 57 that project inwardly from the respective platform rails 56,as also depicted for one possible embodiment by FIG. 5B. Alternatively,platform rails 56 might be configured to provide support and anchoragefor treads 78 directly. It is preferred that the platform rails besituated at the left and right sides of the platform section, with theplatform treads therebetween. However, in other embodiments, theplatform rails might be displaced inwardly from the sides of theplatform section, provided adequate stability can be maintained.

FIG. 3 depicts the guardrail posts 68, 70 as being vertical (i.e.,perpendicular to the surface of the platform treads). In otherembodiments (not shown), the guardrail posts are angulated, so that theybecome approximately vertical with respect to the ground after theplatform system is disposed on a sloped roof. Guardrails 58 are disposedhorizontally at a preselected height above the surface of platformtreads 78 and supported at their ends by lower and upper guardrail posts68, 70. Although the guardrails may be situated at any convenientheight, they typically are positioned in accord with recognized designguidelines or regulatory standards for worker protection. Ordinarily,the height is such that each guardrail can function both as a handrailfor a worker traversing the platform system and to inhibit the workerfrom falling off the side. The guardrails additionally can provide sitesfor anchorage points for worker fall protection equipment, as describedin more detail below.

The guardrail system in some embodiments of the present platform systemfurther comprises a sidewall to afford additional protection, interalia, by inhibiting a prone worker from rolling off the side of theplatform system through the space between the working surface and theguardrails. For example, the sidewall may be provided by screening or byone or more midrails that extend horizontally from the lower to upperguardrail posts and are located intermediate the working surface and theguardrail. Other implementations include optional bracing members in theguardrail system. For example, and without limitation, the sidewall inthe embodiment of FIG. 3 includes cross braces 66 and middle supportposts 72 that further connect guardrails 58 and platform rails 56. Thesebracing members both enhance the structural integrity of the platformsystem and help obscure the opening between the platform surface andguardrails 58 to further inhibit a worker from falling off the platformsystem.

Embodiments may also include toerails located contiguous to the workingarea. In the FIG. 3 embodiment, toerails 74 project perpendicularlyupward from platform rails 56 and extend along the platform length.Toerails enhance safety, both by inhibiting a worker walking on theplatform from stepping off the edge and by reducing the likelihood thatitems on the platform surface, such as tools, equipment, or supplies,would fall from, or be kicked off, the platform sides. In someembodiments, toerails 74 (as well as other portions of the structure)include holes (such as holes 76) to reduce overall platform weight.Toerails may be anchored in any suitable way, including withoutlimitation direct attachment to either the guardrail posts, the platformrails, or the treads. Alternatively, as can be appreciated by referenceto FIG. 5B, the need for separate toerails might be reduced oreliminated by employing a platform rail 56 that is tall enough abovesupport flange 57.

The guardrail system, including the midrails and toerails if present,extends substantially the platform length, meaning that the railingcoverage along the left and right sides of the platform system issufficient to afford fall protection for a worker present anywhere onthe working surface. In most embodiments, the guardrails extendcontinuously between guardrail posts that are attached to the platformrails at or near their respective opposite ends.

In some embodiments, the guardrail system is prepared as a unitaryassembly, meaning that each horizontal guardrail and its associatedupper and lower guardrail posts, and possibly other components, areformed as a single-piece assembly, such as by welding or otherwisepermanently joining multiple components to form the single piece; bybending a single elongated member at its ends to form guardrail postsperpendicular to an intermediate guardrail section; or by any othersuitable manufacturing process. A unitary guardrail assembly may alsoincorporate midrails, cross bracing, middle support posts, toerails, orother desired structural members. Alternatively, separate guardrail andguardrail post members may be connected in a non-unitary assembly by anysuitable form of mechanical attachment, including, without limitation,bolted tube and socket connectors.

The present platform system can readily be equipped with suitableanchorage points for a personal fall arrest system. Such systemstypically include a body belt or harness fitted to a worker and tetheredby at least one rope, cable, chain, webbing strap, or the like to asuitable anchorage point. Once in the appointed working location, theworker attaches the tether to the anchorage point with a releasablelocking clip, such as a carabiner or snap hook. However, the practicalefficacy of any fall arrest system is completely dependent on having aconveniently positioned and anchorage point.

A functioning fall arrest system greatly reduces the likelihood of aserious injury to a worker from in the event of a fall, and may allowtimely rescue and removal of the worker to safety. Many industry andgovernmental standards now require this or comparable protection forworkers at elevated locations.

Adequate safety protection is particularly challenging for workers on aglass-panel greenhouse roof. The solid decking of many conventional roofconstructions means a worker ordinarily is in danger only of fallingonly at the side or edge, whereas a worker on a greenhouse roof can alsofall through the glass panels, with the potential of both lacerationsfrom a broken panel and trauma from hitting structure on the way downand/or the floor or ground below. Suitable anchorage points readily beestablished on a conventional roof, e.g. by attachment to normalstructural members or the roof deck itself, but are ordinarilyunavailable or difficult to access on a glass roof.

An embodiment of the present platform system provides one or moreanchorages for the tethers of a personal fall arrest system. Typically,these anchorages can be provided by any structure to which a lockingclip, such as a carabiner or snap hook, can be removably attached.Ideally, the anchorages are adequate to sustain the load that mightreasonably be expected in a fall or other like foreseeable emergency. Invarious embodiments, the anchorages of the present platform systemcomprise one or more discrete anchorage points that provide an apertureconfigured to render it capable of engaging a locking clip. Useful formsof such discrete anchorage points include, without limitation, eyebolts,and secured free rings having round, oval, d-ring, or other similarlyfunctional shapes. They may be located at any accessible point. In aparticularly convenient embodiment, the platform system comprises aplurality of discrete anchorage points disposed along both guardrails,thereby providing a worker using the platform system one or moreanchorage points located in proximity to the working area with anypossible tread configuration. FIG. 3 depicts a plurality of discreteanchorage points in the form of inwardly-projecting eyebolts 59 that arespaced along guardrails 58. Alternatively, anchorage points might beplaced on the toerails, midrails, or platform treads, or at any othersuitable location. Fall arrest systems could also be anchored directlyto the guardrail or to a free rope separately secured at both ends, e.g.to the guardrails.

The structural integrity of the platform system shown in FIG. 3 is evenfurther enhanced by structure at the platform ends, including upper andlower support bases 79, 80. In a representative intended use, theplatform system is configured to be placed so that at least its uppersupport base, and possibly its lower support base as well, engageload-capable structural members of a sloped, glass-paneled roof system.The platform system and its full load are thus situated on the roof andsupported so that a clearance is maintained underneath at least theworking area and a worker has access to glass panels and other elementsin a desired region of the roof structure. In the FIG. 3 configuration,the support bases 79, 80 respectively comprise upper horizontal member61 and lower horizontal member 60, which are directly connected toplatform rails 56. In other embodiments, the connection between thehorizontal members and the platform rails is made indirectly throughother intervening members. The FIG. 3 structure further comprises sidebraces 62 and gusset braces 64 attached to the horizontal members 60, 61and the guardrail posts 68, 70. The selection, sizing, attachment, andplacement of the various end and side bracing members included in theFIG. 3 embodiment are done in a manner consistent with the desiredcapabilities and requisite strength of the platform system. In variousembodiments, the support bases 79, 80 also include optional upper and/orlower support pads that extend below the horizontal members, of whichsupport pads 86, 87 in FIG. 3 are representative.

FIG. 3 shows the support bases being located at the upper and lower endsof the platform system, but in other implementations one or both arelocated somewhat away from the ends, displaced along the lengthdirection toward the center by any distance that still permits adequatestability to be maintained. One such configuration is depicted by FIG.10, wherein lower support base 80 is located at the lower end of theplatform section, but upper support base 79 is displaced somewhat belowthe upper end.

The lower and upper horizontal members 60, 61 in FIG. 3 are structuredas outriggers that extend laterally to a width greater than the width ofthe platform area itself. Increasing the effective lateral extent of thehorizontal members improves the stability of the platform system againsttipping to the side, both while it is being positioned and when it is inuse and supporting personnel and materiel. Widening the outriggers alsodistributes the loading imposed on the roof structure, due to the weightof both the platform system itself and the personnel and materiel itcarries, over a larger area. However, too high an outrigger span limitsthe placement of the platform system near the edge of a roof, e.g. atthe gable end of a typical sloped roof. In the case of the FIG. 3embodiment, the effective width at the upper end of the platform systemin use is established by the point at which the pair of support pads 86and/or rollers 82 rest on underlying roof structural members.Optionally, the lateral positioning of the pairs of support padsrelative to the platform system (and thus the corresponding pad spacing)is adjustable to accommodate different roof configurations. For example,the point at which support pads 86 are attached to the outrigger portionof upper horizontal member 61, as depicted in FIG. 3, might be madeadjustable.

The present platform system employs platform treads that are removablysecured to the platform rails. For clarity of illustration, FIG. 3depicts only two platform treads 78, one installed onto the platformrails 56 and a second one positioned to be installed. Treads 78 rest onsupport flanges 57 that project inwardly from platform rails 56. It willbe understood that any desired number of platform treads 78 may beinstalled sequentially along platform rails 56 to create the requisiteaccess path, beginning at the lower end of platform section 52 andextending toward the upper end for a preselected distance. The distanceis selected so that a worker can easily position himself for convenientaccess to service a desired section of the roof over or beside which theplatform system is situated. Platform treads 78 are preferably sized topermit the length of the access path to be selected in convenientincrements. Preferably, platform treads 78 are installed with only aminimal gap between adjacent treads to minimize a tripping hazard for aworker ascending the path and to prevent tools, supplies, debris, or thelike from falling through, but some amount of gap is possible.

Any suitable form of tread attachment may be used to removably securethe platform treads. At least one attachment should be providedproximate the left and right edges of each tread, but two or moreattachments may be used on each side to improve the stability and securepositioning of the attachment. In one simple form, the tread attachmentcomprises a threaded fastener system such as a bolt and nut arrangement,with the treads and platform rails having alignable apertures throughwhich the fasteners can be passed and secured. Self-aligningarrangements are preferred for ease of configuration and assembly in thefield.

For example, each platform rail may provide a U-shaped channel having aninwardly-facing opening sized to accept and support platform treads of adesired type. In this configuration, the treads either are slid in fromthe top or bottom end or are placed at the requisite level and rotatedfrom an oblique orientation with respect to the platform length intohorizontal orientation to effect engagement on both sides with theU-channel. Attachment can also be made using threaded fasteners such asa bolt and engaging nut or expanding toggles.

Another tread attachment method (shown in FIG. 4) employs U-shaped stepbrackets 102 spaced regularly along flanges 57 of the opposing platformrails 56 and oriented with their open ends toward the upper end of theplatform system. Suitable treads 78 are dropped into slots provided bythe open ends of step brackets 102. Apertures 106 in the top portion ofeach tread 78 are configured to engage studs 104 upstanding fromplatform rail 56. FIG. 4 depicts one tread already in position and asecond tread inserted in its bracket and ready to be lowered over itscorresponding stud. Optionally, studs 104 are threaded, so a nut (notshown) can be attached after placement of the tread to improve thesecurity of the attachment. Other arrangements for securing the treadsare also contemplated.

Still another form of self-aligning tread attachment is depicted inFIGS. 5A and 5B. For clarity of illustration, FIG. 5A shows a singleattachment point proximate the left edge of representative treads 78 a,78 b, but it will be understood that the treads are similarly attachedon both sides, and preferably at two or more points on each side, toprovide greater stability and security of attachment. This form isparticularly convenient and reliable, because it permits treads to beinstalled and removed quickly and without the need for tools or separatefasteners.

In the implementation depicted, each platform rail 56 comprises aninwardly-projecting support flange 57 configured to support theperipheral edges of platform treads 78 a, 78 b. In FIG. 5A, tread 78 bis shown in full engagement, while tread 78 a is depicted as it is beinginstalled, prior to its final engagement in the position indicated bydotted lines 119.

Still referring to FIGS. 5A and 5B, a plurality of upstanding studs 108are attached at regular intervals along the support flanges 57 on bothsides of the platform. Each stud 108 includes an enlarged, terminal head110 portion and a smaller-diameter shank 112 portion. Each platformtread includes a keyhole-shaped slot 114 having a small-diameter portion116 extending in the platform length direction upwardly away fromlarge-diameter portion 118. Slot 114 is configured for lockingengagement with stud 108.

Head 110 has a diameter such that it can pass through large-diameterportion 118 but not small-diameter portion 116 of slot 114, while shank112 can slide through portion 116. Tread 78 a is shown as being placedso that the large-diameter portion 118 of its keyhole-shaped slot 114 isoriented toward the lower end of the platform and with head 110protruding through slot portion 118. Thereafter, tread 78 a is securedby sliding it downward in the direction D into the position defined bydotted lines 119, so that shank 112 becomes located in portion 116.Tread 78 b is shown in the resulting, fully-engaged configuration. FIG.5B shows in cross-section the full engagement of a stud 108 in a slot114.

The platform treads are fabricated from any suitable material thatprovides sufficient strength, stiffness, and durability. Safety ispromoted by a non-slip top surface on the treads, such as one that issuitably patterned, textured, or roughened. A gritty surface isespecially beneficial for using the platform system in adverse weather.Metal or wood treads can be used, but strong, lightweight compositematerials beneficially reduce weight. For example, a lightweight,non-skid platform tread can be fabricated using a KEVLAR®para-aramid-carbon fiber composite.

Some implementations of the present platform system include an inclinedtop platform tread as the uppermost tread. As depicted in FIG. 7, suchan inclined top platform tread 120 is inclined by an angle φ withrespect to the platform horizontal direction, so that when the platformsystem is erected on a roof sloped upward by approximately the sameangle φ, the surface 122 of the top platform tread 120 is approximatelyparallel to the plane of the ground and a floor of the greenhouse orlike structure. This surface 122 thereby provides a level area on whicha worker can safely and comfortably stand, kneel, or lie whileperforming required tasks. Surface 122 is supported by riser 124, whichextends from base section 126 to surface 122. The same attachment meansused to secure the running platform treads can also be used to securethe inclined top platform tread to the platform rails at the desiredpoint along its length. For example, the FIG. 7 configuration is shownwith keyhole-shaped slots 114 of the same type as seen in FIGS. 5A and5B. It is preferred, but not required, that an inclined top platformtread be longer than the remaining platform treads 78 so that its flatsurface 122 is large enough so that a worker can safely stand, sit, orkneel thereon.

In another variant, some or all of the running platform treads may havean inclined configuration, so that the platform has the generalappearance of a staircase and the platform treads function as stairsteps on which the worker can ascend to the desired level, instead ofwalking up on an inclined, but generally planar, platform path.

The present platform system is appointed to be supported over a roofsystem in a manner that permits it to be used by a worker servicing anarea of the roof beneath. Typically, one or both of the ends of thesystem are configured so that they may bear on capable structuralmembers of the roof, such as the purlins depicted in FIGS. 1-2.Optionally, the lower end may be configured to engage either structureat the eaves 19 of roof side 12, if available, or, alternatively, aladder or scaffold or the like positioned next to side wall 20, e.g. anengagement effected using one or more clamps.

For example, the lower end of the FIG. 3 embodiment includes clamps 77attached to the platform system, e.g., to lower horizontal member 60.Clamps 77 are configured to engage structure that may be available atthe eaves of some greenhouses. The upper end includes upper support pads86 that project downwardly from the upper horizontal member 61. Togetherclamps 77 and upper support pads 86 permit platform system 50 to besecured with its lower end at the eaves and to extend upwardly along thegreenhouse roof with at least its upper support base bearing on theroof's structural members. The platform system is thereby supported, sothat a slight clearance is maintained between it and the underlyingroof. Thus, a worker is enabled to access a desired portion of thegreenhouse roof for construction, maintenance, repair, or likeoperations. It will be understood that clamps 77 may be configured inany form needed to ensure a secure connection to available supportstructure, whether part of the greenhouse structure itself, anindependent scaffold, the deployment assist cart discussed below, orother like structure. Preferably, clamps 77 are attached to the platformsystem by any suitable removable connection, such as bolts, to make thesystem more versatile.

The present platform system optionally, but preferably, includes one ormore retractable roller assemblies that facilitate rolling it into adesired position on a roof surface. The roller assemblies ordinarilyprovide for rolling motion along the platform length direction, but maypermit lateral motion also. Various configurations are possible for therollers, consistent with maneuverability and stability of the platformsystem.

In an implementation, the roller assembly comprises one or moreretractable rollers having a retracted position and an extendedposition. The roller assembly is configured such that when the platformsystem is disposed on a roof structure with the rollers in the retractedposition, at least one support base is in contact with the roofstructure and the body of the platform system remains elevated above theroof structure; in the extended position, the rollers are in contactwith the roof structure and bear against structural members (e.g., atleast two of the glazing bars 32 shown in FIG. 2) and not the glassportion. In an embodiment, the design is such that the platform systemis stable against tilting while it is being moved.

For example, the exemplary embodiment of FIG. 3 provides a rollerassembly that incorporates rollers 82 associated with both upper supportpads 86. With these rollers 82 thus situated on its left and rightsides, platform system 50 can readily be manipulated into position andthereafter stably secured by attaching clamps 77 to suitable supportstructure at its lower end and retracting rollers 82 to bring uppersupport pads 86 into contact with structural members of the roof. FIGS.6A-6B (discussed in more detail below) depict one possible type ofroller assembly.

As noted above, some greenhouses do not include structural members atthe eaves to which the lower end of the present platform system can besecured. In such configurations, the lower end of the system can besecured to an external, temporary support such as a ladder, scaffold, orthe deployment assist cart described below. Alternatively, the systemcan be configured with a lower support base 80 intended (like the uppersupport base 79) to rest on the roof itself. Such embodiments preferablyinclude lower support pads and one or more rollers associated therewith,which are similar to upper support pads 86 and upper rollers 82. Ofcourse, the platform system can employ both a lower support base and anysuitable anchorage to an external support for added security.

Some roller assembly implementations employ a single, relatively wideroller at one or both ends of the platform system. For example, such aroller may extend laterally to at least the full width of the system,and preferably wider, so that the platform system itself is stableagainst tipping laterally and can be moved readily. Alternatively, atleast two rollers, such as separate rollers included at both sides on ofthe one or both ends, are configured to provide similar stability.

In the FIG. 3 configuration, both the rollers 82 and upper support pads86 to which they are attached are laterally displaced from the mainplatform area and deployed on outriggers. As indicated above, thisspacing beneficially improves stability against tipping, both whenmoving the system and when it is supporting a worker during its intendeduse. Ideally, the one or more rollers on each side are sufficiently wideto be able to engage structural members whose spacing can vary widelybetween different roof designs. Alternatively, the lateral span betweenthe rollers in a multi-roller configuration is adjustable. FIG. 3depicts rollers 82 and upper support pads 86 as being conjoined and thusin close proximity, so they can both engage the same roof supportstructure. In other arrangements, the two need not be attached, and maybe separated and adapted to engage different structural members. It isalso contemplated that the lateral spacing of one or both of the rollersand support pads may be adjustable.

In any of these embodiments, each roller is ordinarily rotated on anaxle supported at one or, preferably, both ends. In someimplementations, the axle is supported by a fork having two prongsdependent from a central strut, with the ends of the axle attached tothe respective prongs. Alternatively, one, or preferably both, ends ofthe axle are supported by independent struts. It is preferred, but notrequired, that the axle be in a fixed orientation along the widthdirection of the platform system.

A variety of actuation mechanisms can be employed to move the rollersbetween the extended and the retracted positions. In one option, theaxle support mechanism is hingedly connected to some member of theplatform structure, so that the roller assembly can be moved between theextended position and the retracted position. Various hingingarrangements are possible, including ones in which the roller assemblycan be tilted downwardly from, and along the length of, the platformsystem (e.g., from a horizontal base member), or outwardly (e.g., fromthe platform rails). In another option, a lead screw or gear arrangementcan be used to drive the axle support mechanism between the extended andretracted positions.

In still another option, the actuation relies on a spring mechanismassociated with each roller. The spring mechanism urges the roller intothe extended position, and may include a latching arrangement permittingthe rollers to be locked in either or both of the extended and retractedpositions. In other embodiments, the spring mechanism has a compliancesuch that imposing at least a predetermined weight on the platformsystem is sufficient to overcome the urging into the extended positionand drive the rollers into the retracted position. Typically, thepredetermined weight is some appreciable fraction of the expected weightof a worker, so that the rollers of an unloaded platform system areextended, but reliably move into retracted position once a worker mountsthe platform.

FIGS. 6A-6B depict one such roller assembly, wherein a roller (with anassociated spring mechanism) is associated with a support pad 86. TheFIG. 6 arrangement can be used with the platform system embodiment ofFIG. 3 or other embodiments. Roller 82 is disposed for rotation on anaxle 84, whose opposite ends are attached to struts 88, which aresupported and vertically movable through collinear mating holes 90 inupper and lower axle mounts 92, 93. Upward movement of strut 88 iscountered by a compliant member, such as spring 94 compressed betweenupper axle mount 92 and spring mount 95 attached to strut 88. The springconstant of springs 94 is selected so that loading of the platformsystem with more than a predetermined weight overcomes the downwardurging of rollers 82 by springs 94, so that support pads 86 rest on theunderlying roof structure. FIG. 6B shows roller 82 in its extendedposition below the bottom of upper support pad 86, while FIG. 6A showsroller 82 in its retracted position, with spring 94 compressed and strut88 moved upward from the FIG. 6A configuration.

In a related embodiment (not shown), a retractable roller assembly suchas that of FIGS. 6A-6B is associated with one of the support bases,while the other support base includes one or more non-retractablerollers. For example, platform system 50 of FIG. 3 might be modified tohave retractable roller assemblies of the FIG. 6 type attached tosupport pads 86 on both sides of upper support base 79, but rollersfixed in an extended position on support pads 87 of lower support base80, along with clamps 77 as shown. In use, this form of the platformsystem could rely on being clamped at the roof eaves. Thus, the load ofthe platform system would be distributed, with some carried through theupper support pads 86 and the rest through the clamping of the lowerend.

In the embodiment depicted in FIG. 3, the upper and lower support bases79, 80 are permanently connected to platform section 52. In analternative construction, the system is modularized, meaning that it isconfigured to be assembled from a kit comprising a plurality ofsubcomponents and disassembled again at will, such as on a job site. Themating subcomponents that are to be connected during the assembly arejoined in any convenient but secure and reversible manner.

One possible modularized implementation is shown in FIG. 8, whereinupper and lower end assemblies 98, 99 are separably joined to theplatform section 100 (which includes platform rails 56, guardrails 58,treads 78, and associated bracing components) by any form of secure,locking connection, such as a pin and socket attachment. In thisimplementation, end assemblies 98, 99 comprise support bases 79, 80,which also include horizontal members 60, 61 and optional support padsand roller assemblies that are operable in a manner that is apparentfrom FIGS. 3 and 6. Respective guardrail posts 68, 70 are alsoincorporated in end assemblies 98, 99. The end assemblies are formed byjoining together the various components by any suitable means providingadequate structural integrity. In alternative modularizedconfigurations, the guardrail posts are instead included as part of theplatform section.

The locking connection is provided by connector arrangements that aredisposed at each point of engagement between the end assemblies and theguardrails and platform rails. The FIG. 8 implementation provides fourpoints of engagement at each end of the platform system, i.e., two atthe engagement between the respective left and right guardrails 58 andthe respective guardrail posts 68 and 70 and two at the engagementbetween the left and right platform rails 56 and the horizontal members60 and 61.

Generally stated, each connector arrangement comprises a first connectorelement attached to an end of the respective platform rail or guardrail,a second connector element attached to a respective one of the endassemblies, and a locking means. Typically, one of the connectorelements is a connector pin; the other connector element is a sockethaving a complementary, mating shape adapted to receive the connectorpin. The first and second connector elements are configured to be joinedin mating relationship, with a locking pin securing the mutualengagement of the elements.

The detailed view of FIG. 9 representatively depicts one suitable formof the connector arrangement with reference to the joint at the top ofright upper guardrail post 68 in FIG. 8. Guardrail connector pin 96 aprojects horizontally from upper guardrail post 68 and is configured tobe received in socket 96 b in guardrail 58. After the components areassembled, a through aperture is formed by aligned apertures 96 d inguardrail 58 and 96 e in connector pin 96 a. The locking engagement iscompleted by passing locking pin 96 c through these aligned apertures ina direction perpendicular to the commonly aligned axes of pin 96 a andsocket 96 b. In an alternative locking arrangement, connector pin 96 amight include a spring-loaded pin adapted to project transversely fromthe pin axis to engage an aperture, as depicted at 96 d, in socket 96 b.

Similar locking connections are made at each of points of engagementseen in FIG. 8, wherein guardrail connector pins 96 a attached toguardrail posts 68, 70 are adapted to be received in correspondingsockets 96 b provided in guardrails 58 and platform rail connector pins97 a (also attached to guardrail posts 68, 70) are adapted to bereceived in corresponding sockets 97 b provided in platform rails 56.Each connection is secured by locking pins (not depicted in FIG. 8).Preferably, each of the locking pins is further secured in position byany suitable means known to a skilled designer, including withoutlimitation a cotter pin or by using a threaded form of locking pinsecured by a mating nut.

Locking engagements of the respective platform frame elements arereadily implemented by using tubular members having round or rectangularinternal passages to construct the guardrails and platform rails, withthe connecting pins being of complementary size and shape. Otherimplementations are also suitable, including without limitation ones inwhich the respective disposition of the connector pins and sockets onthe rails and end assemblies is reversed. In still another alternative,pins 96 a and 97 a are omitted and instead, sockets on the endassemblies are configured to directly receive the guardrails andplatform rails with a locking connection.

The modular system of FIG. 8 can easily be disassembled into itscomponent subassemblies (e.g., end assemblies 98, 99; two side sections,each comprising a platform rail 56, a guardrail 58, cross braces 66, andmiddle support posts 72; and a requisite number of platform treads 78,along with needed hardware). Disassembly greatly reduces the bulkinessof the platform system for transportation and storage before subsequentre-use. In addition, the platform section can be used fitted withdifferent forms of the end sections that are adapted to differentgreenhouse constructions.

In most modularized embodiments it is not intended that the componentswithin the end assemblies be disassembled during ordinary operation ofthe platform system. Hence, the techniques used to assemble theend-assembly components can include welding, gluing, or other permanentmethods, as well as other less permanent joining methods such as boltingthe components together to permit repair or replacement of damagedparts. The guardrail and bracing elements of each side rail areordinarily not intended for routine disassembly, and so are joined bysimilar methods.

In a further aspect, the modular concept of the FIG. 8 embodiment can beextended to provide platform systems of varying lengths by connectingmultiple subsections. One representative embodiment is depictedgenerally in FIG. 10, wherein the platform section is divided into twosubsections 100 a, 100 b. Specifically, the platform rails 56 andguardrails 58 shown in FIGS. 3 and 8 are divided into platform railsubsections 56 a, 56 b and guardrail subsections 58 a, 58 b that areconnected through coupling support assembly 130, which has aconfiguration with features generally similar to those of end assemblies98, 99 shown in FIG. 8. Assembly 130 comprises: a middle support base132 having a middle horizontal member 134 and middle support pads 136depending downward therefrom; left and right middle guardrail posts 138connected to middle support base 132; and connector arrangements at thetop and bottom of the left and right middle guardrail posts that securethe facing platform rail and guardrail subsections in collinearrelationship. As depicted, the individual connector pins 96 a of FIGS. 8and 9 are replaced by pairs of oppositely directed connector pins 140 aconfigured to engage mating sockets 140 b in the facing ends of theplatform rail subsections 56 a, 56 b; likewise connector pins 97 a arereplaced by pairs of oppositely directed connector pins 141 a configuredto engage mating sockets 140 b in the facing ends of guardrailsubsections 58 a, 58 b. The connections effected using these mating pins140 a, 141 a and sockets 140 b, 141 b join the platform rail andguardrail subsections together collinearly in a secure, lockingconnection to form the respective platform rails and guardrails.However, intermediate connector arrangements that lack any one or moreof these components are also contemplated, as long as they provide asecure connection between the platform rail subsections of therespective platform subassemblies and ensure that a secure andadequately supported guardrail system protects the entire platform. Forexample, the middle support base might be omitted, with pins alone usedto join subsections 100 a and 100 b. The FIG. 10 embodiment optionallyincludes roller assemblies (not shown) associated with each of thesupport assemblies. The roller assemblies may be of the type depicted inFIGS. 6A-6B or other suitable design.

Implementations such as that of FIG. 10 beneficially facilitate theservicing of large greenhouses, because the platform system can beerected on the roof in stages, instead of having to lift an entiresystem into final position in a single operation. For example, twoplatform subsections (e.g. subsections 100 a, 100 b seen in FIG. 10)might be needed to provide adequate length. Such a platform system canbe erected by first placing onto the roof at the eaves a firstsubassembly comprising upper end assembly 98, platform subsection 100 a,and coupling support section 130. Then a second subassembly comprisingplatform subsection 100 b and lower end assembly 99 can be lifted to theeaves and coupled onto the first. The combined subassemblies can then berolled up the roof till the lower end assembly 99 reaches the eaves andis secured to the desired support structure associated therewith.Modular platform systems comprising more than two subsections are alsocontemplated herein. Use of individual subsections that are as long aspossible, consistent with a handleable weight, is generally beneficial,since the number of joints can be minimized and the overall structure ismore rigid and less subject to flexure at each joint.

In a still further aspect of the present disclosure, a deployment assistcart is used in conjunction with the platform system to provide aplatform erection system. Such a cart may be used to facilitate theerection of the platform system onto a greenhouse roof. The cart mayinclude wheels or tracks, so it can be moved to a desired site adjacentto a roof structure to be serviced. Preferably the cart is also used totransport the platform system components. It optionally provides astable and secure attachment for the lower end of the platform system,since many greenhouses do not have a suitable structure to which thelower end can be secured.

FIG. 11 depicts a representative embodiment, including cart 160 havingwheels 162 that permit it to be easily maneuvered and locked into aconvenient position. Once the cart is positioned, outrigger stabilizers164 are projected downwardly, e.g. by a reversible jackscrew mechanism(not shown), so that the weight of the cart and whatever load itsupports are transferred off the wheels and onto support pads 165 ofstabilizers 164. Cart 160 is optionally provided with suitable handlesto permit it to be maneuvered into position by a worker. Alternativelythe cart may be transported by attaching it to a vehicle through a hitch(not shown).

Cart 160 is equipped with deployment support 168, which upstands fromplatform base section 169, and ordinarily is braced either by anoptional access ladder 166 as shown in FIG. 11 or by other suitablebracing structure. Support 168 may be oriented either exactlyperpendicular to base section 169 or at a preselected angle away fromthe vertical direction. In the FIG. 11 embodiment, access ladder 166 anddeployment support 168 are stabilized by securing their respective basesto the platform base section 169 of cart 160 and joining them at a pointabove the platform base section, preferably at or near their tops.Optionally, access ladder 166 and deployment support 168 are removablefor ease of transport. In another variant (not shown), ladder steps areincorporated directly in deployment support 168, so a separate accessladder is not needed. Deployment support 168 may also include clamps orother like fixturing to provide stable and secure anchorage for thelower end of the platform system after it has been deployed on a roof,as mentioned above.

Cart 160 further includes deployment rails configured to facilitate theerection of the platform on a roof. In a representative use, the cart isfirst positioned at the desired location. Then the platform system isstaged on the deployment rails and thereafter deployed onto the adjacentroof. The entire system may be erected in one operation; alternatively,sections of a modular system may be positioned in a series of steps. Therails beneficially may be equipped with rollers, guides, slides, or thelike that engage the platform components while they are being erected.(For clarity of illustration, the deployment rails are omitted from FIG.11.) It is preferred that the deployment rails, if present, be tiltable,but embodiments wherein the rails are fixed at an inclination anglesuitable for positioning the platform system are also possible. The cartand deployment rails may include a winch, hydraulics, or other likeactuation system to assist in elevating the deployment rails and/orsliding the platform system onto the roof structure.

Referring now to FIGS. 12A-12C, the stages of a representative andtypical use of deployment assist cart 160 are depicted. For convenienceof illustration, the cart is shown as being used to erect asingle-section platform system, such as the embodiment 50 depicted byFIG. 3, on a sloped greenhouse roof surface 12. A pair of tiltabledeployment rails 170 are rotatably articulated at or near the top ofdeployment support 168. In some embodiments, the point of articulationof rails 170 and/or the height of deployment support 168 can beadjusted. The articulation permits the rails to be elevated between aloading position 171 a and a deployment position 171 b (shown bydot-dash lines in FIG. 12A). A suitable mechanism (not shown) ispreferably provided to permit the deployment rails to be locked at oneor more requisite elevations.

In a first configuration shown in FIG. 12A, cart 160 is situated on theground near the eaves 19 where the platform is to be erected, the cartbeing secured by deploying its outrigger stabilizers 164. Platformsection 50 is placed against rails 170 in loading position 171 a. Thenrails 170 and platform section 50 secured thereon are rotated downwardlyto an elevation approximately parallel to the plane of the sloped roof,e.g. to deployment position 171 b, with the top ends of the railspossibly resting upon the eaves (FIG. 12B). Platform section 50 is thenmaneuvered, e.g. by sliding or rolling it upward on rails 170 and ontothe roof structure (FIG. 12C). Once in place, platform section 50 issecured, e.g. by clamping its lower end to either part of the roofstructure at or near eaves 19 or to any convenient structural member ofcart 160. A worker may ascend ladder 166 to access the platformstructure. If needed, a gangplank can be used to bridge any gap betweenthe ladder and the platform itself.

Alternatively, the rails 170 might be disposed initially in deploymentposition 171 b and then platform section 50 placed thereon, bypassingthe rotation connecting the FIGS. 12A and 12B configurations.

It will be apparent that the cart embodiment seen in FIGS. 11 and 12 canalso be used to erect a multi-section platform system by a sequence ofsteps, wherein separated subassemblies of the platform system areelevated one by one and assembled as they are moved into position on theroof. For example, the first subassembly 100 a of FIG. 10 can be erectedin a manner comparable to that described above, by sliding it up rails170 and temporarily securing it on the roof so that coupling supportsection 130 is proximate the eaves. Then rails 170 are rotated back toloading position 171 a to receive a second subassembly comprisingplatform subsection 100 b and lower end assembly 99. The rails are thenraised again into deployment position 171 b, along with the secondsubassembly, which is joined onto the first subassembly using theconnector arrangements associated with coupling support section 130. Thecombined subsections can then be slid upwardly into position on theroof, with the bottom end of the second subassembly being secured eitherto structure at the eaves or to a ground-positioned support such asvertical ladder support 168 or other structural member of cart 160, orto a conventional ground-situated ladder, scaffold, or the like. Asimilar process can be used to erect a platform having more than twosubassemblies by sequentially repeating pertinent ones of the foregoingsteps. The platform may be removed by reversing the foregoing steps.

It is desirable that the platform system be strong enough to accommodatethe weight of a single worker and a desired payload of tools, equipment,and supplies needed for typical maintenance or repair operations.However, it is further preferred that the platform system be strongenough to support a second person, for example to assist or rescue thefirst worker in an emergency situation.

In certain embodiments, the present platform system beneficially has astrong but lightweight construction. Minimizing the platform's weightmakes it easy to transport, assemble, and situate on a roof, while alsoreducing the load that is imposed onto the roof system during its use.Ideally the platform weight is a small fraction of the aggregate weightof a worker and their payload. It is further desirable that a platformsystem be light enough that a small work crew can readily erect andmaneuver it into position, all without damaging a glass roof. Systemsthat can be handled by a two-person crew are beneficial, especially ifthe platform system can be erected on the roof without a crane or anelaborate or specialized hoist system.

In an embodiment, a platform system in accordance with the presentdisclosure is constructed with materials having high specific strengthand stiffness. These characteristics are most readily attained withadvanced composite materials, however it is to be understood that anystructural material (e.g. metals) can also be employed in one or morecomponents of low-weight embodiments. Suitable light-weight materialsinclude, without limitation, composites with one or more of glass,carbon, or other polymers or polymeric fibers. Embodiments fabricatedwith members composed of a composite with KEVLAR® para-aramid/carbonfiber reinforcement in an epoxy matrix provide a beneficial combinationof the required high specific strength and stiffness. Such compositescan be manufactured in various shapes useful in constructing the presentsystem, including without limitation round, square, and rectangulartubular forms and flat, planar panels. The various components can bejoined using any suitable technique or joint hardware.

Certain embodiments of the present platform system are capable ofsupporting a rated load of at least 500 pounds or 200 kg while beinglight-weight. Such a platform system having an unloaded weight “W”(i.e., including a complete set of platform treads but excluding workersand other payloads) and a full platform working area “A” is consideredto be light-weight if a value of the ratio W/A is at most 3, 4, 5, 6, 7,8, 9, or 10 pounds per square foot of working area.

The load of the platform system and its payload is supported over a roofarea that may be larger than the platform working area, particularly forembodiments wherein the support bases include outrigger supports. Theeffective support area is at least as large as the area of a polygonhaving vertices defined by each of the points on which the platformsystem rests atop a roof or like structure. For example, theconfiguration depicted by FIG. 3 may be supported over a rectangulareffective support area defined by the four support pads 86, 87.Alternatively, if the FIG. 3 configuration is clamped at its bottom endby clamps 77 attached to a rail structure (not shown) at the eaves of agreenhouse, the effective support area might be defined by a trapezoidhaving vertices at clamps 77 and upper support pads 86.

For example, a representative platform system embodiment of the formdepicted by FIG. 3 might have a full working area 16 feet (˜4.9 m) longand 30 inches (˜75 cm) wide and be supported by upper and lower supportbases that are located at the platform system's upper and lower ends andhave outriggers that extend to a width of 10 feet (˜3 m). Such anembodiment can be constructed with KEVLAR® para-aramid/carbon fiberreinforced composite members and platform treads, and be strong enoughto support a rated load of at least 500 pounds (˜227 kg or 2230 N).Platform treads spanning the 30 inch platform width and extending about12 inches (˜30 cm) along the platform length would weigh about 4 pounds(˜1.8 kg or 17.8 N) each. This platform system, with a full set ofplatform treads installed along its length, would have a total weight ofabout 230 pounds (˜104 kg or 1023 N), corresponding to about 5.75 poundsper square foot of working area (275 N/m²).

The 230 pound weight of the platform system and treads of thisembodiment is supported over an effective support area on the roof of160 square feet (10 foot outrigger span×16 foot length), correspondingto an effective roof loading of about 1.44 pounds per square foot (69N/m²) of effective support area. Even with a worker, tools, andmateriel, the system thus imposes a roof loading far less than thebuilding code requirement that a greenhouse in the Delaware location ofthe inventors must be capable of withstanding a snow loading of 20-25pounds per square foot (˜958-1197 N/m²). In representative embodiments,the present platform system, including a full set of platform treads butwithout a user or any other payload, imposes an effective roof loadingof at most 1.2, 1.4, 1.6, 1.8, 2, or 2.5 pounds per square foot ofeffective roof support area.

It is noted that design standards in the ladder and scaffold industriestypically presume a safety factor of at least 5, meaning the devicewould be presumed able to withstand a loading of five times the ratednameplate load. The safety factor thus accounts for variations instrength of the actual device as constructed and possibly degradedduring its lifetime and the need to support an additional worker who maybe forced to aid the primary user in the event of an injury, medicalemergency, fire, or other unforeseen circumstance.

Having thus described various embodiments of the invention in ratherfull detail, it will be understood that this detail need not be strictlyadhered to but that further changes and modifications may suggestthemselves to one skilled in the art, all falling within the scope ofthe invention as defined by the subjoined claims. For example, certainmaterials are identified herein as suitable for constructing componentsof the present platform system, but other materials known to a skilledartisan may also be used. Various structural configurations and assemblymethods that are suitable are also known to the artisan.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, where an embodiment of thesubject matter hereof is stated or described as comprising, including,containing, having, being composed of, or being constituted by or ofcertain features or elements, one or more features or elements inaddition to those explicitly stated or described may be present in theembodiment. An alternative embodiment of the subject matter hereof,however, may be stated or described as consisting essentially of certainfeatures or elements, in which embodiment features or elements thatwould materially alter the principle of operation or the distinguishingcharacteristics of the embodiment are not present therein. A furtheralternative embodiment of the subject matter hereof may be stated ordescribed as consisting of certain features or elements, in whichembodiment, or in insubstantial variations thereof, only the features orelements specifically stated or described are present. Additionally, theterm “comprising” is intended to include examples encompassed by theterms “consisting essentially of” and “consisting of.” Similarly, theterm “consisting essentially of” is intended to include examplesencompassed by the term “consisting of.”

When any amount or other value or parameter is given as either a range,preferred range, or a list of upper preferable values and lowerpreferable values, this is to be understood as specifically disclosingall ranges formed from any pair of any upper range limit or preferredvalue and any lower range limit or preferred value, regardless ofwhether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. It is not intended that the scope of the invention be limitedto the specific values recited when defining a range.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, amounts, sizes, ranges,formulations, parameters, and other quantities and characteristicsrecited herein, particularly when modified by the term “about”, may butneed not be exact, and may also be approximate and/or larger or smaller(as desired) than stated, reflecting tolerances, conversion factors,rounding off, measurement error, and the like, as well as the inclusionwithin a stated value of those values outside it that have, within thecontext of this invention, functional and/or operable equivalence to thestated value.

What is claimed is:
 1. A platform system elongated along a platformlength direction between a lower end and an upper end and havingopposing left and right sides separated along a platform widthdirection, the platform system being configured for placement on a roofstructure and comprising: (a) left and right upper-end guardrail postsand left and right lower-end guardrail posts; (b) a platform sectionthat extends along the platform length direction for a platform lengthand comprises: (i) left and right platform rails that are disposed inspaced-apart, parallel relationship and extend horizontally along thelength of the platform section between the upper and lower ends of theplatform system, the upper-end guardrail posts and the lower-endguardrail posts being attached to the respective platform rails, (ii) aplurality of platform treads disposed along at least a portion of theplatform length, each tread having left and right edges and spanning theleft and right platform rails and being removably secured thereto, thetreads collectively defining a working platform area having a platformwidth sufficient to accommodate a worker and a preselected workinglength defined by the number of treads present, and (iii) left and rightguardrails that extend horizontally along the respective sides of theplatform system for substantially the platform length, are attached tothe respective left and right platform rails through the lower and upperguardrail posts, and are situated at a preselected height above theplatform area; (c) an upper support base proximate the upper end andcomprising an upper horizontal member; and (d) a lower support baseproximate the lower end and comprising a lower horizontal member, andwherein the upper and lower support bases project downward from theplatform section and are configured to rest on the roof structure tosupport the platform system and maintain a clearance between the roofstructure and the platform section.
 2. The platform system of claim 1,further comprising a roller assembly associated with the upper supportbase, the roller assembly comprising one or more rollers having aretracted position and an extended position, the roller assembly beingconfigured such that when the platform system is placed on a roofstructure: (a) with the rollers in the retracted position the uppersupport base is in contact with the roof structure; and (b) with therollers in the extended position the rollers are in contact with theroof structure and the upper support base is elevated above the roofstructure, thereby permitting the platform system to be rolled along theplatform length direction.
 3. The platform system of claim 2, whereinthe roller assembly comprises a spring mechanism that is operable tourge the one or more rollers downward into the extended position and hasa compliance such that imposition of at least a predetermined weight onthe platform system is sufficient to overcome the downward urging anddrive the one or more rollers into the retracted position.
 4. Theplatform system of claim 2, wherein the roller assembly comprises atleast two rollers, one of the at least two rollers being situated oneach of the left and right sides of the platform system.
 5. The platformsystem of claim 1, further comprising a roller assembly associated witheach of the upper and lower support bases, each roller assemblycomprising one or more rollers having a retracted position and anextended position, the roller assemblies being configured such that whenthe platform system is placed on a roof structure: (a) with the one ormore rollers in the retracted position the support bases are in contactwith the roof structure; and (b) with the one or more rollers in theextended position the rollers are in contact with the roof structure andthe support bases are elevated above the roof structure, therebypermitting the platform system to be rolled along the platform lengthdirection.
 6. The platform system of claim 5, wherein each rollerassembly comprises a spring mechanism that is operable to urge the oneor more rollers of the roller assembly downward into the extendedposition and has a compliance such that imposition of at least apredetermined weight on the platform system is sufficient to overcomethe downward urging and drive the one or more rollers of each rollerassembly into the retracted position.
 7. The platform system of claim 1,further comprising a plurality of tread attachments, at least one ofwhich is disposed proximate each edge of each of the platform treads toremovably secure the platform treads to the platform rails.
 8. Theplatform system of claim 7, wherein each tread attachment comprises astud having an enlarged head and upstanding from one of the respectiveplatform rails, and at least one keyhole-shaped slot is providedproximate each edge of each platform tread, each keyhole-shaped slotbeing configured for locking engagement with one of the studs.
 9. Theplatform system of claim 1, further comprising a plurality ofanchorages, each configured to engage a locking clip of a personal fallarrest system.
 10. The platform system of claim 9, wherein theanchorages comprise one or more discrete anchorage points spaced alongeach of the guardrails and attached thereto, each anchorage pointproviding an aperture configured to engage the locking clip.
 11. Theplatform system of claim 1, wherein the upper-end guardrail posts andthe upper support base are formed as an upper end assembly and thelower-end guardrail posts and the lower support base are formed as alower end assembly, and the upper and lower end assemblies are separablyjoined to the platform section by connections made at points ofengagement between the guardrails and the platform rails and the endassemblies.
 12. The platform system of claim 1, being capable ofsupporting a rated load of at least 200 kg and having a ratio of anunloaded weight “W” of the platform system to a full working area “A”that is at most 8 pounds per square foot of working area.
 13. Theplatform system of claim 1, wherein the left and right platform railsand the left and right guardrails are each comprised of a plurality ofsubsections that are collinearly disposed and separably joined togetherin a locking connection to form the respective platform rails andguardrails.
 14. The platform system of claim 13, further comprising: acoupling support assembly situated intermediate the upper and lower endsand comprising a middle support base comprising a middle horizontalmember and left and right middle guardrail posts connected to the middlesupport base, and wherein respective subsections of the platform railsand the guardrails are separably joined together through lockingconnections made using connectors disposed at points of engagement onthe coupling support assembly.
 15. The platform system of claim 14,wherein each of the connectors comprises a first connector elementattached to an end of the respective platform rail or guardrailsubsection, a second connector element attached to the coupling supportassembly, and a locking pin, the connector elements being configured tobe joined in mating relationship and secured to each other by mutualengagement with the locking pin, the first connector element being oneof a connector pin and a mating socket and the second connector elementbeing the other of the connector pin and the mating socket.
 16. Aplatform erection system, comprising the platform system of claim 1 anda deployment assist cart comprising: (a) a platform base section; (b) adeployment support upstanding from the platform base section; (c)deployment rails connected to the deployment support and configured toreceive the platform system for deployment on a roof structure.
 17. Theplatform erection system of claim 16, wherein the deployment rails arerotatable between a loading position configured to accept the platformsystem and a deployment position configured to permit the platformsystem to be maneuvered from the deployment rails onto a surface of theroof structure.
 18. A method of providing access to a structure,comprising: (a) providing a platform system as recited by claim 1; and(b) disposing the platform system on a flat or sloped area of thestructure, whereby access is provided to the area.
 19. A kit, comprisingparts that, when assembled, are capable of forming the platform systemof claim
 1. 20. The kit of claim 19, further comprising parts that, whenassembled, are capable of forming a deployment assist cart comprising:(a) a platform base section; (b) a deployment support upstanding fromthe platform base section; (c) deployment rails connected to thedeployment support and configured to receive the platform system fordeployment on a roof structure.